NCursesUI: refactor info_show code
NCursesUI: refactor info_show code

Show MenuDoc info on the left of the menu if necessary. Cleanup the
code.

occivink/kakoune,alexherbo2/kakoune,jkonecny12/kakoune,jjthrash/kakoune,Somasis/kakoune,casimir/kakoune,occivink/kakoune,casimir/kakoune,danr/kakoune,Somasis/kakoune,danr/kakoune,occivink/kakoune,Somasis/kakoune,Somasis/kakoune,mawww/kakoune,lenormf/kakoune,occivink/kakoune,alexherbo2/kakoune,danr/kakoune,jkonecny12/kakoune,jjthrash/kakoune,lenormf/kakoune,danr/kakoune,casimir/kakoune,jkonecny12/kakoune,mawww/kakoune,casimir/kakoune,alexherbo2/kakoune,jjthrash/kakoune,lenormf/kakoune,mawww/kakoune,mawww/kakoune,jjthrash/kakoune,jkonecny12/kakoune,lenormf/kakoune,alexherbo2/kakoune